Synthesis of glutamic acid



United States Patent SYNTHESIS OF GLUTAIVHC ACID Oscar L. Norman, Northbrook', 111., assignor to Internafi onal; Minerals & Chemical Corporation, a corporation of New York No Drawing. Application September .25, 1957' Serial No. 686,018

9. Claims, (Cl. 260-3263) The pr sent inv n ion rela es to t e preparation of glutamic acid. More particularly, it relatesto the'sy lrnon oxidizing g n such as ni i id, chromic cid,

potassium permangante, and the like. In order to aveid loss of .theamin o p d ng u h oxi ati n, Su li an found it, nece a y t pre e t the amino gro p by rea ing it with a-carboxylic acid to form th am de t e! oi; and

after xid t on, it as nece sary to. emo e he "Prote ive g oup y ydr lysi unde o e ona c nditions- The n cessity for. carrying ou hese addi i nal one et ona as well as the expenditure of proces materials therein, Q9119 e it t a ev r e n mic u d on the o er l process Ihn e now de el p an mp oved tech iqu for effec ing e c v on of A -QYGlQP I DYBELiBQ hioh :for convenience will e. r ed to reinafter a or ered tenylam ne) o DL py ro i o ee rhexylio eeidand D s u temie aci Specific lly, Lhe eto ndhat the de ired con ersi n n b ach e ed by st con erting :eyclopen y mine int a oye openteny arn nonium .salt s of. a strong acid, j cting the sa t to .O LQ iZatliDH' ainxsuspen: sion or preferably in solution in a suitable solvent, cleaving the ozonization product under oxidizing conditions to produc a m x ure of -glu mie aeidandDLhy Another object is to convert cyclopentenylamine into an ozonization product which-can be converted into glutamieaci by x a i e leav ge nd hyd olysis! Another object is to improve the oxidative conversion of ey lop ntenylam ne in DL- gln amie snid-v Other objects of the inventionwillbe apparent from the present descritpion and claims. 1 v

Th p p rati n: of eyelop teny-lar in ison eniently arri u for p e, 'by on n ngl nefi ehloroeyolee pentenc, methylene chloride, and liquid-ammonia in about; 1 l :4 weight ratio in a pressure vessel ,at Dry- Icetentper, ature, sealing the vessel, and allowing ito warm termini; temperature. At: theend of around 3Q minllteS-atrt1mti temper nr o emmoniaiis vented from thevcs: e n s -p s am oniiu rchl r de is filtered from th p o ct; ea g a solution at cyclopcntenylamine'in 1 mflre rapid ratestthe. losses o'f-ozone frcnythe-system a d Au 1s, 1.252

m thylene chlor de.- Othe so e s m y, of ur be utilized in the prepa at The ey op n y ami e a conveniently e, isolated, if desired, by fractional distillatio rby pr p tat n with anhy rous yd o en hlor e or other stro the a In a c rdan th my invention a i t r f y l nen nyl m ne wi h a i ble solvent is: ao d with sulfuricv acid, phosphoric acid, tI C 0r d a d 01" other strong acid, uref hly y r ge ch or e, to corn e 't the a 'i into the corr p d n ye open enylem mon tn s t, af eh'en zo -c n i g g s pa sed through the mixture until the, cyclopentenylammonium salt has been substantially completelyozonized, Any-solvent can be. used which dissolves the QYGIQPentenyIammon nin sa t-at e st'to's m t n t bly aronnd"2% byw isht rmore); h ch does not nde netion dur ns; t e ozo e treatment, a d hi h doe no adv rse y afie t h .ou.r-s o the anoniza ion rea on I prefer ten e lower alipha ic fatty aei such as formic acid, aee ieeoidinrouionie ac d. .o he like; o a owersal ha i deo oLsut h a met anol, ethanol, isopr py alcohol, n-hu l aleoh hor he ike: The. p op rt n of e i em teny ntrn n urn salt t -solvent may vary widely, nd e n. eenvenientlyrange from abo 5 o about Wi ht, Q 1 he total mixture.

T Q QZQQi dfiQn is convenientlycarried ou'tby passing m .ture, elf-929 and a idiluenttgas unaife'cted bythe ozonization reaction, suitably air, oxygen, or an inert gas such assnitrogen, The concentration of ozone in the gaseq sr'niixtureis not critical, but the use of pure ozone one highcouoentration of ozone-may result in a waste of this material if the equipment or rate of flow-does not permit adequate contact between the ozone and the-cycle pentenylammoniurn salt. I ordinarily prefer-to employ azstream ofoxygen containing betweenabout 2 and about 15%. byweight-ofsozone. Lowerconcentrations of ozone are undesirable, because: such concentrations undulyextend thereaction time, I v The. ozonization ris -most conveniently-carried out at ordinary temperature, i.e., around lite 40 v('3. Higher temperatures maybe employed but tend to cause degradation of the cyclopentenylarnine. Considerably loweri emperature-may also-beiemployed, as -low as about V #15: (3., .but .:are:not.-ordinarily justifiable on an eco{ nomicbasiss r a Th631'fl116i0f addition of ozone to the reaction mixture id not critical, and. can be carried out at any "convenient; andpreasonable rate .underthe existingoo1'1 ilit ions.- At

because: fiincompletereaction tend to increase, while, t. slew rates t the time rcquired for complete ozonizati'on" is. extended; -32In'. aany v event, the passage of ozone ti re-uglithe reaction mixture is continued until ozone appears -1n' Substantial proportions of the exit-gases, thus'indi'c'ating:

that l the i cyelopentenylammonium salt has "been jsub'stana tlally :cempletely reacted The 'introductioi ofozone is then discontinued; T1

-j (The. productof the ozone tneatment is presumablyfjan -ozonide...andiwill be referredtohereinassuch, 1haye hereinafter. V V

= iomizetion p duct mixture is subjected to oxida' 1 reflwh eintnuimmy dream about 50 to "about notiisolated .orfoharacterized ithis material; however, and not certain as to its identityer structure; "Whatever itsgnaturepit -is-' readily convertedinte pyrrolidoncear boxylic agidnand vglutamic aeid by theyrocedurefdesm tionbto :cleave and to selectivelyoxidize -the-oionid employing aselective oxidizing-agent to eftc't ,-n

estrma'tive -oxidation,- atee'levated 'temperatures up to C, In

acid, or by other meansv well known in through the cyolopentenylammonium salt mixture a dry a preferred technique, the ozonization product is added to glacial acetic acid, then treated with air or oxygen until the solution becomes free from active oxygen (i.e., fails to liberate iodine from potassium iodide). For this purpose, a mixture of oxygen with a catalytic amount of ozone (around 0.01 to 0.1%) is especially desirable. In another technique, the ozonization product is acidified (unless already acidic) with sulfuric acid, hydrochloric acid, formic acid, acetic acid, or the like, then admixed with hydrogen peroxide, and heated at about 75 to about 100 C. for about /2 to about 5 hours. The concentration of hydrogen peroxide should preferably be at least about 30% by weight, optimally about 50%, and the proportion of hydrogen peroxide to ozonide should be at least equirnolar. Other oxidizing, agents can also be employed, such as cupric oxide, hypochlorous acid, sodium hypochlorite, potassium permanganate, oxides of nitrogen, and the like.

The oxidized ozonization product comprises a mixture of DL-glutamic acid and DL-pyrrolidonecarboxylic acid, which can be separately recovered if desired by means well known in the art. In one technique, any volatile organic acids, such as formic acid or aceticacid, are removed by fractional distillation, azeotropic distillation, or by other suitable means. Inorganic acids, such as sulfuric acid, are neutralized and/or removed, e.g., by precipitation with barium hydroxide or other suitable base. Any solids resulting therefrom are filtered 0d. The filtrate is adjusted to pH 3.2, the DL-glutamic acid is allowed to crystallize, and the crystals are filtered off. The filtrate is extracted with an ester such as ethyl acetate, which selectively removes the pyrrolidonecarboxylic acid. Other techniques for the separation may be employed, as disclosed in the art.

The crude oxidation product can also be treated to convert the DL-pyrrolidonecarboxylic acid therein-into DL-glutamic acid by hydrolysis under acid or basic conditions well known to the art. After hydrolysis, the DL-glutamic acid can be recovered from the hydrolyzat by crystallization at its iso-electric point.

The salts employed in my invention are the reaction products of cyclopentenylamine and a strong acid, i.e., an acid having an ionization constant of at least about at 25 C., preferably a strong mineral acid; 3 t e The following operating examples will more clearly illustrate my invention.

Example 1 Preparation of cyclopentenylamine.-To a 250-ml.

autoclave, which had been cooled in crushed Dry'Ice, were successively added 100 ml. of liquid ammonia and a solution (cooled to CL) of 1 5.2 g. of 3-chloro cyclopentene in 15 g. of toluene, anhydrous conditions being maintained as nearly as possible. The autoclave was sealed and allowed to come to ambient temperature (about 29 C.) and ambient pressure (118 p.s'.i.g.), where it wasallowed to remain for about 30 minutes. The unreacted ammonia was then vented, and the autoclave was unloaded and washed 'with three 10-m'l. portions of toluene- The product and washings werecombinedand filtered to, remove the solid-phase ammonium'chloride; Two additional batches were prepared according to the same procedure, and the filtrates were combined and heated on a steam bath under a reflux condenser fo'r hour to drive oh? the remaining ammonia. The deam moniated solution was cooled inan .ice. bath, and-hydro gen chloride gas was bubbled into it untilti grams had been absorbed, at which point an excess Ofhydmgen chloride appeared to bepresent The resultingpre cipi which wasremoved for solubility ,tests).was-dissolved in 40 of ethanol with heating. The solution wasdecbl:

. 4 orized with activated carbon and filtered hot, and the carbon cake was washed with 10 ml. of ethanol. The filtrate and washings were diluted with 150 ml. (3 vol.) of ethyl ether, and cyclopentenylammonium chloride was allowed to crystallize therefrom in white needles. The crystals were filtered off, washed with ethyl ether, and air dried. The purified product weighed 14.5 grams and analyzed as follows:

Theory, percent Found, percent Cl- 29. 6 29. 84 N 11.7 11.51

Ozonization of cyclopentenylammonium chloride- Cyclopentenylammonium chloride (1.2 g., 0.01 mole) was dissolved in 15 ml. of glacial acetic acid, and through the solution was bubbled a stream of oxygen containing about 4% ozone at the rate of about 30 liters per hour and at a temperature around 25 C. The ozonization was complete at the end of 20 minutes. The treated solution was added to a solution of 0.1 m1. of sulfuric acid in 20 ml. of glacial acetic acid. To the resulting solution was added a mixture of 15 ml. of glacial acetic acid and 0.6 ml. of aqueous 50% hydrogen peroxide. The total mixture was heated to 90 C. over a period of 45 minutes, during which time it began to darken. After an additional 15 minutes at 90 C. a potassium iodide test for active oxygen was negative. The solution was then cooled, 1 ml. of 28% ammonium hydroxide was added, and the mixture was evaporated to dryness. The dry residue was dissolved in water, made up to a total volume of 50 ml., and analyzed for L-glutamic acid by the decarboxylase method (Seidman & Blish, J. Ag. & Food Chem. 5 (1957), 448). An aliquot was subjected to acid hydrolysis under conventional conditions and the hydrolyzate was analyzed for L-glutamic acid. The first analysis is a measure of the L-glutamic acid in the product, while the difierence between the first and second analyses represents the pyrrolidonecarboxylic acid produced by the process. Before hydrolysis the solution contained 0.8 mg./ml. of L-glutamic acid, equivalent to 0.08 g. of DL-glutamic acid, or a yield of 5.4% based oncyclopentenylamine. After hydrolysis, the product solution contained 4.2 mg./ml., equivalent to 0.42 g. 'of DL-glutamic acid, or a yield of 28.6%.

Example 2 The ozonization and subsequent procedure of Example 1 were repeated except that the oxidation was carried out with 1.8 ml. of aqueous 50% hydrogen peroxide at a temperature below 85 C. The oxidized solution was amber in color, and was found to contain 2.4 rug/ml. of L-glutamic acid, equivalent to 0.24 g. of DL-glutamic acid, or a 16.3% yield based on cyclopentenylamine. After hydrolysis, the product solution contained 5.1 mgj/ml. of L-glutarnic acid, equivalent to 0.51 g. of DL- glutamic acid, or a yield of 34.7%.

Example 3 additional 5-ml. portion of glacial acetic acid. The solution'rwas ozonized at 23 C. with about 4% ozone in oxy gen at a flow rate of about 30 liters per hour, 20 minutes being required-to complete the ozonization. The treated solution'was added to a mixture ofO.l ml. of sulfuric acid and 20 ml. ofglacial acetic acid, then a mixture of 0.8ml.

. of.50% hydrogen peroxide in 15 ml. of glacial acetic acid was added, and the tot'al mixture was heated slowly tof ZCOVI a period of about one hour. During the-heat ing, a suspended immiscible phase cleared up at 65 C. After about 10 minutes at 90 C., a potassium iodide test for active oxygen was negative. The solution was then cooled, commingled with 2 ml. of 28% ammonium hydroxide solution, and evaporated to dryness. The residue was dissolved in water, made up to 50 ml. and analyzed as in Example 1. Before hydrolysis, the solution contained 0.88 mg./ml. of L-glutarnic acid, equivalent to 0.088 g. of DL-glutamic acid, or a yield of 5.8%, based on cyclopentenylamine. After hydrolysis, the product contained 1.0 mg./rnl., equivalent to 0.10 g. of DL-glutamic acid, or a yield of 6.3%.

Example 4 Ozonization of cyclopentenylammonium phosphate. To a solution of 1.65 g. (0.02 mole) of cyclopentenylamine in 20 ml. of ethyl ether were added 2.3 g. of 85% orthophosphoric acid dropwise with stirring and with sufficient cooling to keep the ether from volatilizing. The resulting crystals of cyclopentenylammonium phosphate were filtered off, dried, and found to weigh 3.7 g. (theo. 3.62 g.). The crystals were dissolved in 25 ml. of glacial acetic acid, and the solution was treated at 25 C. with 4% ozone in oxygen at a flow rate of about 30 liters per hour, 35 minutes being required to complete the ozonization. The treated solution was commingled with 0.3 ml. of sulfuric acid in 28 ml. of glacial acetic acid, then a mixture of 1.6 ml. of 50% hydrogen peroxide in 15 ml. of glacial acetic acid was added, and the total mixture was heated at 90 C. for 3.5 hours. At the end of this time a potassium iodide test for active oxygen was negative. The solution was then cooled, commingled with 2 m1. of 28% ammonium hydroxide solution, and evaporated to dryness. The residue was hydrolyzed by refluxing in 40 ml. of aqueous 20% hydrochloric acid for 4 hours. The hydrolyzate was evaporated to small volume to remove the hydrogen chloride. The residue was dissolved in water, made up to 100 ml., and analyzed as in Example 1. The solution was found to contain 0.88 mg./ ml. of L-glutamic acid, corresponding to 0.166 g. of DL- glutamic acid, or a yield of 5.6%.

Example 5 Oxygen cleavage of ozonide-A solution of 4.8 g. (0.04 mole) of cyclopentenylammonium chloride in 40 ml. of glacial acetic acid was ozonized at 25 C. with 4% ozone in oxygen at a flow rate of about 30 liters per hour, about 1.3 hours being required to complete the ozonization. The treated solution was further oxidized by passing a stream of oxygen containing about 0.05% ozone through said solution while slowly raising the temperature to 60 C., 30 minutes being required to reach this temperature. During this time, the solution darkened and the potassium iodide test for active oxygen became negative. The acetic acid was distilled off and the residue was hydrolyzed by refluxing with 80 ml. of aqueous 20% hydrochloric acid for 4 hours. The hydrolyzate was evaporated to low volume to remove the hydrochloric acid, and the residue was dissolved in water, made up to 100 ml., and analyzed as in Example 1. The solution was found to contain 4.59 mg./ml. of L-glutamic'acid, corresponding to 0.918 g. of DL-glutamic acid, or a yield of 15.6%.

While the foregoing examples illustrate certain specific embodiments of the invention, together with specific starting materials, processing materials, and operating steps and conditions, it is to be understood that such matters are illustrative only, and are not in any way intended as a limitation upon the scope of the invention. Numerous modifications and equivalents will be apparent from the foregoing description to those skilled in the art.

In accordance with the foregoing description, I claim as my invention:

1. A process for preparing pyrrolidonecarboxylic acid which comprises subjecting a solution of a strong acid salt of M-cyclopentenylamine to contact'with an ozonecontaining gas until the absorption of ozone by said solution substantially ceases, cleaving the resulting ozonization product under oxidizing conditions, and recovering pyrrolidonecarboxylic acid therefrom.

2. A process for preparing glutamic acid which comprises subjecting a solution of a strong acid salt of A cyclopentenylamine to contact with an ozone-containing gas until the absorption of ozone by said solution substantially ceases, cleaving the resulting ozonization product under oxidizing conditions, whereby a mixture of glutamic acid and pyrrolidonecarboxylic acid is obtained, subjecting said mixture to hydrolysis, and recovering DL-glutamic acid from the hydrolyzate.

3. A process which comprises treating a solution of a strong acid salt of A -cyclopentenylamine in an organic solvent with an ozone-containing gas until the absorption of ozone substantially'completely ceases, cleaving the resulting ozonization product with an oxidizing agent at a temperature between about 50 and about C., hydrolyzing the oxidized ozonization product, and recovering DL-glutamic acid therefrom.

4. The process of claim 3 wherein said salt is A cyclopentenylammonium chloride.

5. The process of claim 3 wherein said salt is A- cyclopentenylammonium sulfate.

6. The process of claim 3 wherein said salt is A'- cyclopentenylammonium phosphate.

7. A process which comprises treating a solution of a mineral acid salt of A -cyclopentenylamine in an inert solvent therefor with an ozone-containing gas at a temperature between about 15 and about 40 C. until the absorption of ozone substantially ceases, decomposing the resulting ozonide with air containing a catalytic proportion of ozone at a temperature between about 50 and about 150 C., hydrolyzing the treated product, and recovering DL-glutamic acid therefrom.

8. The process of claim 7 in which said solvent is acetic acid.

9. A process which comprises treating a solution of a. mineral acid salt of A -cyclopentenylamine in an inert solvent therefor with an ozone-containing gas at a temperature between about 15 and about 40 C. until the absorption of ozone substantially ceases, decomposing the resulting ozonide by heating with hydrogen peroxide, hydrolyzing the treated product and recovering DL- glutamic acid therefrom.

References Cited in the file of this patent UNITED STATES PATENTS 2,791,606 Novak et a1. May 7, 1957 2,801,250 Sullivan July 30, 1957 2,833,786 Purvis May 6, 1958 

1. A PROCESS FOR PREPARING PYRROLIDONECARBOXYLIC ACID WHICH COMPRISES SUBJECTING A SOLUTION OF A STRONG ACID SALT OF $2-CYCLOPENYLAMINE TO CONTACT WITH AN OZONECONTAINING GAS UNTIL THE ABSORPTION OF OZONE BY SAID SOLUTION SUBSTANTIALLY CEASES, CLEVING THE RESULTING OZONIZATION PRODUCT UNDER OXIDIZING CONDITIONS, AND RECOVERING PYRROLIDONECARBOXYLIC ACID THEREFROM. 